Donald Trump has kept the world on edge with a trade policy that seems to change by the day. So far, American consumers have been shielded from much of the impact. But as the world of international shipping adjusts to his policies, the president is facing a potential reckoning.

With the US-China trade war starting to gum up container traffic between the world’s two biggest economies, freight companies are warning of plunging bookings and a surge in “blank sailings” – where ports are skipped or voyages are called off altogether. Earlier this week, America’s most powerful retail executives trooped into the White House to deliver a blunt prognosis: tariffs on Chinese goods risked causing “empty shelves” in two weeks without a change of course. The three companies who attended the meeting – Walmart, Target and Home Depot – are among the most exposed to the president’s policies, which include tariffs of up to 145pc on Chinese goods and higher port fees for Chinese-made vessels.

Walmart sources roughly 60pc of its imports from China, including clothing, electronics and toys, according to Reuters’ research, while around 50pc of Target’s suppliers are also based there.